For pathology investigations, stained specimens or tissue samples, such as a histological section, are secured on specimen slides and equipped with a coverslip. The specimens coverslipped in this fashion can then be investigated under a microscope. Coverslippers, in which mounting of the coverslip or coverslipping of the individual specimen slides occurs in an automated process, are especially suitable for mounting the coverslips onto the microscopic specimen slides. For this process, multiple specimen slides having tissue samples are placed into compartments or slots of a rack or specimen slide holder. The rack having the specimen slides is coupled to a coverslipping unit where each specimen slide is removed from the rack and a mounting medium, an adhesive, or the like is applied onto the specimen slide. The coverslip is then mounted onto the specimen slide in order to seal off the tissue sample on the specimen slide.
Placement of the coverslip onto the specimen slide requires an accurate alignment of the coverslip and specimen slide in order to ensure that the coverslip is precisely positioned on the specimen slide. The reason is that if the coverslip protrudes laterally beyond the specimen slide, there is a risk of damage to or destruction of the coverslip. The person conducting the subsequent analysis might also sustain injury from the protruding coverslip.
DE 699 26 803 T2 has already disclosed an apparatus for coverslipping specimen slides that comprises, at the top end of a transport carriage, an entrainment disk that removes a specimen slide from a rack and conveys it to a coverslipping position. During transport, a mounting medium is applied onto the specimen slide. In the coverslipping position, a coverslip from a magazine is then mounted onto the specimen slide. Correct alignment of the specimen slide with respect to the coverslip is said to be ensured by the fact that the dimensions of the components, and the mutual spacings between the coverslip magazine and the coverslipping position, are coordinated with one another.
An apparatus, known from DE 10 2008 047 575 A1, for coverslipping specimen slides provides means with which the rest position of the specimen slide in space relative to the coverslip can be aligned in order to ensure correct positioning of the components with respect to one another. For this, the specimen slide is arranged in its coverslipping position in a special receiving region of a base frame. The base frame comprises a sensor unit that senses spatial deviations between the coverslip and specimen slide. Adjusting screws, which modify the relative position between the coverslip magazine and the base frame, are actuated on the basis of the deviation values. The relative position of the coverslip in the base frame cannot, however, be corrected in this context. Misalignments that occur in this position can cause the coverslip mounted onto the specimen slide to be skewed, and the coverslipped specimen slide can thereby be damaged.